[PATCH] fix OOM killing of swapoff

These days, if you swapoff when there isn't enough memory, OOM killer gives
"BUG: scheduling while atomic" and the machine hangs: badness() needs to do
its PF_SWAPOFF return after the task_unlock (tasklist_lock is also held
here, so p isn't going to be freed: PF_SWAPOFF might get turned off at any
moment, but that doesn't really matter).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/oom_kill.c

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 6969cfb..b278b8d 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -61,12 +61,6 @@
 	}
 
 	/*
-	 * swapoff can easily use up all memory, so kill those first.
-	 */
-	if (p->flags & PF_SWAPOFF)
-		return ULONG_MAX;
-
-	/*
 	 * The memory size of the process is the basis for the badness.
 	 */
 	points = mm->total_vm;
@@ -77,6 +71,12 @@
 	task_unlock(p);
 
 	/*
+	 * swapoff can easily use up all memory, so kill those first.
+	 */
+	if (p->flags & PF_SWAPOFF)
+		return ULONG_MAX;
+
+	/*
 	 * Processes which fork a lot of child processes are likely
 	 * a good choice. We add half the vmsize of the children if they
 	 * have an own mm. This prevents forking servers to flood the